SAAB 9-5 BATTERY PROBLEM

2003 SAAB 9-5 • 110,000 miles

2.0T the car will start but dosent idel well then after just a few secods it dies out. Now I have replaced the battery altinator and plugs any sugestions. A friend thinks it could be a coil pack or an injector but Im sinking lots of money into this and need some other ideas.